Thesis and Guide details:
Details of CSIR Fellowship/ Associateship held, if any or from other sources/ agencies.
Significant foreign assignments:
(a) Significant contributions to science and/ or technology development by the nominee
based on the work done in India during most part of last 5 years:
A major focus of the research carried out by the nominee has been the development of a versatile system of motile colloids, which is of current fundamental (active matter, soft matter physics) and technological(microfluidics, biophysics, drug delivery) interest. The experimental system is based on helical magnetic nanostructures (nanoswimmers [1]) dispersed in fluidic environments, which can be maneuvered under the action of rotating/oscillating magnetic [2] fields. Over last few years, the nominee has made various important
contributions in understanding and expanding the scope of this powerful nanosystem.
Dynamics of the magnetic nanoswimmers: The group led by nominee carried out detailed experimental study
of the dynamics [3] of the nanoswimmers, performed numerical simulations, and derived analytical [4] formula
that explains the experimental observations accurately. They have discovered chaotic bistable dynamics under
certain experimental conditions, which was a surprising observation considering this was a typical low
Reynolds number environment but could be understood from the numerical and analytical studies. They
studied the effect of thermal fluctuations [5] on the motion of the nanoswimmers and predicted the size below
which helical propulsion is rendered useless. The study consisted of both theoretical and experimental
aspects, which will impact the design of practical nano-propulsion systems. Crucially, the study of the
dynamics has given rise to an interesting technology [6] (patent applied), where the propellers could be used to
measure mechanical properties (viscosity) of complex (e.g. shear thinning) and heterogeneous fluidic
environments with very high spatial resolution and extremely high speed.
From driven system to all magnetic active matter: Standard helical propulsion with externally applied torques
results in motion whose direction is tied to the characteristics of the driving torque. This contrasts with selfpropelled
systems, such as living bacteria or catalytic swimmers, whose directions are entirely governed by
orientation diffusion and fluidic interactions. For making intelligent nanoscale systems, the constituents need to
be self-propelled. This fundamental limitation for the helical swimmers was overcome by developing an all
magnetic active matter, which was also the first demonstration of a “reciprocal swimmer” [7]. An interesting
extension of this idea has allowed them to demonstrate independent positioning [8] of two nanoswimmers that
are of identical shape and size. Extending upon the method to obtain reciprocal motion, now the nominee has
devised a method to operate this system as non-reciprocal swimmers (manuscript under preparation) as well.
Considering their interaction to be mainly hydrodynamic in nature, with a level of activity that can be tuned
externally, surely this novel system of artificial swimmers will provide a powerful platform to investigate active
matter phenomena. During these studies, they have discovered an interesting self-purification [9] phenomenon
where external (passive) dopants were found to permanently internalize or spontaneously eject out of a host
system (here, confined colloidal crystallites) depending on the position of the dopant. New interesting
phenomena are expected to emerge from these studies, which have been extended to active hosts and dopants (using nanoswimmers: manuscript in preparation).
Biological environments, including intracellular spaces: There are plenty of biomedical applications possible with the magnetic nanoswimmers, and surely this patented [10] technology is moving toward clinical studies within a few years.
(b) Impact of the contributions in the field concerned:
The contributions made by the nominee on magnetic nanoswimmers is mostly applied in nature, where several
new technologies have been developed, which typically originated from a detailed investigation of certain
fundamental phenomena. For example, investigation of the rigid body dynamics of the swimmers under
external torque [3] led to analytical expressions [4] which incorporated the rheological parameters of the
surrounding medium. These expressions formed the basis of a new microrheological technique [6] that are
applicable to Newtonian and shear-thinning media. A similar example is related to attempts made by the
nominee to make the system self-propelled [7], which in turn led to a new nanomanipulation technique, where
the swimmers can be positioned independently [8] in microfluidic devices. On fundamental side, the
development of an all magnetic self-propelled system based on helical swimmers will be of great interest to the
active matter community.
Similarly, the nominee investigated the limits of electromagnetic near field enhancement for a plasmonic dimer,
for which he developed an experimental system comprising of a novel dimer-graphene sandwich configuration.
While this study provided great insight into the details of near field enhancement, it also resulted in record
enhancement of graphene photoresponsivity [19], which is important in 2D material based optoelectronic
technologies. The integration of plasmonics with helical nanostructures not only resulted in metamaterials with
strong chiro-optical response [16] but have also resulted in the development of a mobile nanotweezer [20]
which can lead to novel and impactful microfluidic technologies pertaining to colloidal manipulation and
nanoscale assembly.
Undoubtedly, the biggest impact of the nanoswimmers in the long term will be in the field of targeted drug
delivery, for which he has made crucial contributions. The nominee has led an interdisciplinary group of
scientists to achieve voyage of the swimmers through human blood [11] and inside living cells [13]. The
experience in maneuvering through such important biological media will surely be followed by deploying these
nanoprobes in live animals, and hopefully someday in humans.
Apart from magnetic nanoswimmers and plasmonics, a certain aspect of the research carried out by the
nominee has very strong fundamental value. While certain interesting results came by chance, as was the
discovery of self-purification of colloidal crystallites [9], the nominee has developed a research program on
multielectron bubbles or MEBs in liquid helium over last few years. The goal of this research program is to
discover quantum melting of a Wigner crystal in 2D, and MEBs are promising candidates as an experimental
system for observing these phase transitions. In an important breakthrough, the group led by the nominee was
able to trap the MEBs [21] using a Paul trap, which may be a crucial step in achieving these ambitious goals.
Places where work of last 5 years has been referred/ cited in Books, Reviews:
Names of the industries in which the technology (ies) has (have) been used :
The achievements already been recognised by Awards by any learned body:
The Awardee a fellow of the Indian National Science Academy/Indian Academy of Sciences/National
Academy of Sciences/Others:
The Awardee delivered invited lecture(s) in India/abroad and/or chaired any scientific
Internatiional Conference Symposium:
List of Awardee's 10 most significant publications.
List of Awardee's 5 most significant publications during the last 5 years
List of Awardee's 5 most significant publications from out of work done in India
during the last five years:
Complete list of publications in standard refereed journals:
Complete list of publications with foreign collaborators (indicating your status
as author):
List of papers published in Conferences /Symposia/ Seminars, etc:
List of the most outstanding Technical Reports/ Review Articles:
Statement regarding collaboration with scientists abroad:
Total number of patents granted in last five years.
Details of Books published: